1. Field of the Invention
The present invention relates to a semiconductor device, in particular, the present invention relates to an organic light emitting device (OLED) having a light emitting element formed on a substrate having an insulating surface. Further, the present invention relates to an organic light emitting module on which ICs and the like, including a controller, are mounted to an organic light emitting panel. Note that the terms organic light emitting panel and organic light emitting module both refer to light emitting devices in this specification. The present invention additionally relates to an apparatus for manufacturing the light emitting device.
In this specification, semiconductor devices correspond to general devices functioning by use of semiconductor characteristics. Therefore, a light emitting device, an electro-optical device, a semiconductor circuit and an electronic device are all included in the category of the semiconductor device.
2. Description of the Related Art
Techniques of forming TFTs (thin film transistors) on substrates have been progressing greatly in recent years, and developments in their application to active matrix display devices is advancing. In particular, TFTs that use polysilicon films have a higher electric field effect mobility (also referred to as mobility) than TFTs that use conventional amorphous silicon films, and therefore high speed operation is possible. Developments in performing control of pixels by forming driver circuits made from TFTs that use polysilicon films on a substrate on which the pixels are formed have therefore been flourishing. It has been expected that various advantages can be obtained by using active matrix display devices in which pixels and driver circuits are mounted on the same substrate, such as reductions in manufacturing cost, miniaturization of the display device, increases in yield, and increases in throughput.
Furthermore, research on active matrix light emitting devices using organic light emitting elements as self light emitting elements (hereinafter referred to simply as light emitting devices) has become more active. The light emitting devices are also referred to as organic EL displays (OELDs) and organic light emitting diodes (OLEDs).
TFT switching elements (hereinafter referred to as switching elements) are formed for each pixel in active matrix light emitting devices, and driver elements for performing electric current control using the switching TFTs (hereinafter referred to as electric current control TFTs) are operated, thus making EL layers (strictly speaking, light emitting layers) emit light. For example, a light emitting device disclosed in JP 10-189252 A is known.
Organic light emitting elements are self light emitting, and therefore have high visibility. Backlights, necessary for liquid crystal display devices (LCDs), are not required for organic light emitting elements, which are optimal for making display devices thinner and have no limitations in viewing angle. Light emitting devices using organic light emitting elements are consequently being focused upon as substitutes for CRTs and LCDs.
Note that EL elements have a layer containing an organic compound in which luminescence develops by the addition of an electric field (electroluminescence) (hereinafter referred to as EL layer, an anode, and a cathode. There is light emission when returning to a base state from a singlet excitation state (fluorescence), and light emission when returning to a base state from a triplet excitation state (phosphorescence) in the organic compound layer, and it is possible to apply both types of light emission to light emitting devices manufactured by the manufacturing apparatus and film formation method of the present invention.
EL elements have a structure in which an EL layer is sandwiched between a pair of electrodes, and the EL layer normally has a laminate structure. A “hole transporting layer/light emitting layer/electron transporting layer” laminate structure proposed by Tang et al. of Eastman Kodak Co. can be given as a typical example. This structure has extremely high light emitting efficiency, and at present almost all light emitting devices undergoing research and development employ this structure.
Further, a structure in which: a hole injecting layer, a hole transporting layer, a light emitting layer, and an electron transporting layer are laminated in order on an anode; or a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injecting layer are laminated in order on an anode may also be used. Fluorescent pigments and the like may also be doped into the light emitting layers. Further, all of the layers may be formed by using low molecular weight materials, and all of the layers may be formed by using high molecular weight materials. The layers may also include inorganic materials such as silicon.
Note that all layers formed between a cathode and an anode are referred to generically as EL layers in this specification. The aforementioned hole injecting layer, hole transporting layer, light emitting layer, electron transporting layer, and electron injecting layer are therefore all included in the category of EL layers.
Both low molecular weight organic compound materials and high molecular weight (polymer) organic compound materials are undergoing research as organic compound materials for EL layers (strictly speaking light emitting layers) which can be regarded as a main EL element.
Ink jet methods, evaporation, and spin coating are known as methods for forming films of these organic materials.
However, with these methods the film formation precision is not very high. Wide gaps are therefore designed between different pixels, and insulators referred to as banks are formed between pixels, when considering the manufacture of full color, flat panel displays using red, green, and blue colors of light emission.
Further, the demands for high definition, high aperture ratio, and high reliability are increased for full color flat panel displays using red, green, and blue color light emission. These demands become a big problem, however, in that the pitch between pixels becomes finer along with making the light emitting device higher in definition (increasing the number of pixels) and reducing the size of the light emitting device. Furthermore, the demands for increases in productivity and reductions in cost also increase.